What is the best way to save async data in Vue?

Question

I have a following store module:

const state = {
    user: {}
}

const mutations = {
    saveData(state, payload) {
        state.user = payload
    }
}

const actions = {
    async loadData({ commit }, payload) {
        try {
            const res = await axios.get('https://api.example.com/user/1')
            commit('saveData', res.data.data)
        } catch(e) {
            console.log(e)
        }
    } 
}

const getters = {
    getData(state) {
        return state.user
    } 
}

Now what's the best way to save the data in component? Is it using watch

import { mapGetters } from 'vuex'

export default {
    data() {
        return {
            user: {}
        }
    },
    computed: {
        ...mapGetters({
            getData
        })
    },
    watch: {
        '$store.state.users.users'() {
            this.user = this.getData
        }
    }
}

... or store.subscribe?

import { mapGetters } from 'vuex'

export default {
    data() {
        return {
            user: {}
        }
    },
    computed: {
        ...mapGetters({
            getData
        })
    },
    created() {
        this.$store.subscribe((mutation, state) => {
            if(mutation.type === 'saveData') {
                this.user = this.getData
            }
        })
    }
}

Answer 1

Since you already know about store mapping I suppose you try to have some kind of edit form where you need the actual data taken from the database and also the ability to change this data to later send it back to the database.

You don't need a getter to have a simple reference to a store item. You will be very fine with mapState in your component:

{
  computed: {
    ...mapState({
      user: state => state.user,
    }),
  }
}

So as soon as user changed in the store your component will know about it. And here you can update the object you're editing. Let's rename it to edit to avoid collision:

{
  data() {
    return {
      edit: {},
    }
  },

  computed: {
    ...mapState({
      user: state => state.user,
    }),
  },

  watch: {
    user: {
      immediate: true,
      handler(user) {
        this.edit = { ...user }
      },
    },
  },
}

Now edit is updated accordingly even if the component was mounted after the store item was updated (thanks to immediate option), and you can safely modify it in your component without any impact on the store reference.

PS Have to mention that in this implementation if you want to have reactivity on fields within edit object, then you need to update the whole edit object on each it's field update like this: this.edit = {...this.edit, [prop]: value} . But if you want it to be the natural Vue way, then first you need to initialize edit with actual object structure, and in the watcher for user perform something like Object.assign(this.edit, user) .

Answer 2

It's preferable to use computed properties to access store data and keep it reactive. It's possible to create a computed property using mapGetters as you do in the shared snipped, however, taking into account the getter is simply returning user from state, I don't think you need a getter at all, you can simply map the value from state by using mapState helper. In this way the component would be simplified to something like as follows:

import { mapState } from 'vuex'

export default {
    computed: {
        ...mapState([
            'user'
        ])
    }
}

With the above approach you can reference user as this.user in the component's methods or simply as user in template of the component. Also, since the getter is out of use, you can delete the getter definition from the store (unless you are using it anywhere else).